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Date:      Wed, 14 Jul 2004 17:56:37 +0400
From:      Yar Tikhiy <yar@comp.chem.msu.su>
To:        Jean-Sebastien Roy <js@jeannot.org>
Cc:        marck@rinet.ru
Subject:   Re: Silent errors when reading CDs
Message-ID:  <20040714135637.GB18493@comp.chem.msu.su>
In-Reply-To: <40F52FD1.9040908@jeannot.org>
References:  <40EF172C.7020508@jeannot.org> <20040713233120.GA79064@comp.chem.msu.su> <40F52FD1.9040908@jeannot.org>

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On Wed, Jul 14, 2004 at 03:06:25PM +0200, Jean-Sebastien Roy wrote:
> 
> >Once I had an old noname PC (iP200 in an i430VX motherboard), and
> >I installed a DVD+RW drive into it.  Data read from a CD or DVD was
> >damaged with high probability.  With hw.ata.atapi_dma set to zero,
> >the probability of data corruption was lower, but still noticable.
> >That's while there were no corruption on burning in DMA or PIO mode.
> >
> At least I'm not alone !

Of course you are not!  A lot of ATA users are in the same boat.
I myself managed to get out of it only thanks to VIA ;-)  Now I
have a VIA KT133-based motherboard, which seems to have no trouble
with DMA on ATAPI.  Alas, it doesn't mean that other VIA chipsets
have bug-free ATAPI support.  Moreover, it won't guarantee that
another instance of the same chipset would give you no trouble.

> >Are there CDs in your collection that produce no errors?
> >
> Yes, but I cannot really tell if it's by chance or they really do not 
> produce errors.

That's a point to test in order to be completely sure.  Just pick
such a "error-free" CD, read it *really many* a time, and compare
the checksums.

> The CDs read well in other computers. FWIW, my ATA controler is an Intel 
> ICH5 :
[skip]
> I think I will live with this bug until I change hardware.

In any case, testing the effect of disabling atapi_dma in your
system would be interesting.

-- 
Yar



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